Many applications benefit from temperature monitoring for a variety of purposes. For instance, it is desirable to monitor temperature in the food and pharmaceutical industries for products that are sensitive to temperature exposure. Certain foods or pharmaceuticals can lose useful lifetime when exposed to high temperatures. Other applications, such as electronics applications, may also be susceptible to undesirable temperature-related effects.
Referring particularly to applications involving perishable products, a forward reaction rate exhibits an Arrhenius type of dependency, such that a shelf-life of food, pharmaceutical product or other perishable product is exponentially responsive to temperature. It can be desirable to detect or monitor such exponential decay as an indication of the quality of perishable product being monitored. While various approaches exist to capture exponential decay, such approaches can undesirably require a power source. Further, many applications are difficult to implement with powered circuits. For instance, hazardous environments may not be amenable to power supplies. Many environments are difficult to access, and monitoring may be otherwise expensive to implement with powered (e.g., battery) applications, such as for monitoring individual food or pharmaceutical packages.
These and other matters have presented challenges to temperature monitoring, for a variety of applications.